Zoom lens and imaging apparatus

ABSTRACT

The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression is related to lateral magnification of the fourth lens group and a lateral magnification of the sixth lens group is satisfied.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. patent application Ser.No. 16/220,104 filed on Dec. 14, 2018, which claims priority under 35U.S.C. § 119 to Japanese Patent Application No. 2017-244501, filed onDec. 20, 2017. The above application is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a zoom lens and an imaging apparatus.

2. Description of the Related Art

In the related art, in an interchangeable lens to be used in a digitalcamera, there is a need for a so-called zoom lens with a high zoom ratiocapable of performing imaging by using one lens without interchangingthe lens from a wide angle region to a telephoto region. For example,JP2017-134302A and JP6189637B describe a zoom lens that takes cognizanceof a high zoom ratio available for a digital camera.

SUMMARY OF THE INVENTION

Since such a zoom lens with a high zoom ratio which does not require theinterchange of a lens is useful in a situation in which a user does notwant to carry a plurality of lenses, that is, a situation in which theuser does not want to increase their luggage, there is a need for asmall zoom lens. Since the zoom lens with a high zoom ratio is used inimaging such as imaging in a wide composition from a wide angle totelephoto and imaging in a wide range from distant view to near view, itis desirable that high-quality images are able to be obtained in allthese situations. In recent years, the number of imaging pixels of theimaging element used by being combined with the zoom lens increases, andadvanced aberration correction is required in the zoom lens.

However, the zoom lens described in JP2017-134302A has a problem that itis difficult to compose a small lens system since a backfocus and thetotal length of the lens are long even though the backfocus and thetotal length of the lens are converted by using the size of the imagingelement as a reference. The zoom lens described in JP6189637B has aproblem that it is difficult to secure high quality from the distantview to the near view since fluctuation in aberration during focusing ishigh.

In view of such circumstances, an object of the present invention is toprovide a zoom lens which achieves reduction in size and has highoptical performance obtained by satisfactorily correcting variousaberrations with regard to imaging over the entire zooming range andfrom distant view to near view while securing a high zoom ratio, and animaging apparatus comprising the zoom lens.

In order to solve the problems, a zoom lens according to the presentinvention comprises only six lens groups, as lens groups, which consistof a first lens group having a positive refractive power, a second lensgroup having a negative refractive power, a third lens group having apositive refractive power, a fourth lens group having a negativerefractive power, a fifth lens group having a negative refractive power,and a sixth lens group having a positive refractive power, in order froman object side to an image side. All distances between adjacent lensgroups in an optical axis direction change during zooming, a stop isdisposed between a lens surface of the second lens group closest to theimage side and a lens surface of the fourth lens group closest to theimage side, the first lens group consists of a negative lens, a positivelens, and a positive lens in order from the object side to the imageside, a lens group moving during focusing is only the fourth lens group,and the fourth lens group moves to the image side during focusing froman object with a long range to an object with a short range, andassuming that a lateral magnification of the fourth lens group at atelephoto end during focusing on an object at infinity is β4T, a lateralmagnification of the fourth lens group at a wide-angle end duringfocusing on the object at infinity is β4W, a lateral magnification ofthe sixth lens group at the telephoto end during focusing on the objectat infinity is β6T, and a lateral magnification of the sixth lens groupat the wide-angle end during focusing on the object at infinity is β6W,Conditional Expression (1) is satisfied.1.5<(β4T/β4W)/(β6T/β6W)<2.5  (1)

In the zoom lens according to the present invention, it is preferablethat Conditional Expression (1-1) is satisfied.1.75<(β4T/β4W)/(β6T/β6W)<2.25  (1-1)

In the zoom lens according to the present invention, assuming that afocal length of the first lens group is f1 and a focal length of thesixth lens group is f6, it is preferable that Conditional Expression (2)is satisfied and it is more preferable that Conditional Expression (2-1)is satisfied.0.95<f1/f6<1.9  (2)1.1<f1/f6<1.7  (2-1)

In the zoom lens according to the present invention, assuming that afocal length of the second lens group is f2 and a focal length of thesixth lens group is f6, it is preferable that Conditional Expression (3)is satisfied, and it is more preferable that Conditional Expression(3-1) is satisfied.−0.28<f2/f6<−0.11  (3)−0.25<f2/f6<−0.14  (3-1)

In the zoom lens according to the present invention, assuming that alens of the third lens group closest to the object side is a positivelens and an Abbe number of the positive lens of the third lens groupclosest to the object side at a d line is ν3f, it is preferable thatConditional Expression (4) is satisfied, and it is more preferable thatConditional Expression (4-1) is satisfied.25<ν3f<49  (4)28<ν3f<45  (4-1)

In the zoom lens according to the present invention, assuming that alens of the third lens group closest to the image side is a positivelens and an Abbe number of the positive lens of the third lens groupclosest to the image side at a d line is ν3r, it is preferable thatConditional Expression (5) is satisfied, and it is more preferable thatConditional Expression (5-1) is satisfied.57<ν3r<97  (5)62<ν3r<87  (5-1)

In the zoom lens according to the present invention, it is preferablethat a lens of the third lens group closest to the image side is apositive lens and image shake correction is performed by moving thepositive lens of the third lens group closest to the image side in adirection crossing an optical axis.

In the zoom lens according to the present invention, assuming that adistance on an optical axis between a lens surface of the third lensgroup closest to the image side at a wide-angle end and a lens surfaceof the fourth lens group closest to the object side at the wide-angleend is D34W and a distance on the optical axis between a lens surface ofthe third lens group closest to the image side at a telephoto end and alens surface of the fourth lens group closest to the object side at thetelephoto end is D34T, it is preferable that Conditional Expression (6)is satisfied or it is more preferable that Conditional Expression (6-1)is satisfied.0.2<D34W/D34T<1.2  (6)0.3<D34W/D34T<1  (6-1)

In the zoom lens according to the present invention, it is preferablethat all lens surfaces of the sixth lens group have shapes convex towardthe image side.

In the zoom lens according to the present invention, assuming that anaverage of Abbe numbers of positive lenses within the first lens groupat a d line is ν1pave, it is preferable that Conditional Expression (7)is satisfied.67<ν1pave<97  (7)

In the zoom lens according to the present invention, it is preferablethat the third lens group consists of a single lens having a positiverefractive power, a single lens having a positive refractive power, acemented lens obtained by cementing a negative lens and a positive lensin order from the object side, and a single lens having a positiverefractive power in order from the object side to the image side.

In the zoom lens according to the present invention, it is preferablethat the fourth lens group consists of a cemented lens obtained bycementing a positive lens and a negative lens in order from the objectside.

In the zoom lens according to the present invention, it is preferablethat the fifth lens group consists of a single lens having a negativerefractive power.

In the zoom lens according to the present invention, it is preferablethat the sixth lens group consists of a single lens having a positiverefractive power.

An imaging apparatus according to the present embodiment comprises thezoom lens according to the present invention.

In the present description, it should be noted that the terms“consisting of ˜” and “consists of ˜” mean that the imaging lens mayinclude not only the above-mentioned elements but also lensessubstantially having no refractive powers, optical elements, which arenot lenses, such as a stop, a filter, and a cover glass, and mechanismparts such as a lens flange, a lens barrel, an imaging element, and acamera shake correction mechanism in addition to the illustratedconstituent elements.

In the present description, the term “˜ group that has a positiverefractive power” means that the group has a positive refractive poweras a whole. Likewise, the term “˜ group that has a negative refractivepower” means that the group has a negative refractive power as a whole.The “lens having a positive refractive power” and the “positive lens”are synonymous. The “lens having a negative refractive power” and the“negative lens” are synonymous. The “lens group” is not to limit to aconfiguration consisting of a plurality of lenses, and may consist ofonly one lens. The “single lens” means one lens which is not cemented.Here, a complex aspherical lens (a lens functions as one aspherical lensas a whole by integrally forming a spherical lens and an aspherical filmformed on the spherical lens) is not regarded as a cemented lens, and istreated as one lens. It is assumed that a reference sign of a refractivepower related to a lens including an aspherical surface and a surfaceshape of a lens surface are considered in paraxial region unlessotherwise noted. The “focal length” used in Conditional Expressions is aparaxial focal length. Values in Conditional Expressions are values in acase where the d line (a wavelength of 587.6 nanometers (nm)) is used asa reference in a state in which the object at infinity is in focus.

According to the present invention, it is possible to provide a zoomlens which achieves reduction in size and has high optical performanceobtained by satisfactorily correcting various aberrations with regard toimaging over the entire zooming range and from distant view to near viewwhile securing a high zoom ratio, and an imaging apparatus comprisingthe zoom lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a lens configuration and amovement locus of a zoom lens (a zoom lens according to Example 1)according to an embodiment of the present invention at a wide-angle end.

FIG. 2 is a cross-sectional view illustrating a configuration andoptical paths of the zoom lens according to Example 1 of the presentinvention at a wide-angle end, a middle focal length state, and atelephoto end.

FIG. 3 is a cross-sectional view illustrating a lens configuration and amovement locus of a zoom lens according to Example 2 of the presentinvention at the wide-angle end.

FIG. 4 is a cross-sectional view illustrating a lens configuration and amovement locus of a zoom lens according to Example 3 of the presentinvention at the wide-angle end.

FIG. 5 is a cross-sectional view illustrating a lens configuration and amovement locus of a zoom lens according to Example 4 of the presentinvention at the wide-angle end.

FIG. 6 is a cross-sectional view illustrating a lens configuration and amovement locus of a zoom lens according to Example 5 of the presentinvention at the wide-angle end.

FIG. 7 is a diagram of aberrations of the zoom lens according to Example1 of the present invention during focusing on an object at infinity.

FIG. 8 is a diagram of aberrations of the zoom lens according to Example1 of the present invention during focusing on an object at a finitedistance.

FIG. 9 is a diagram of aberrations of the zoom lens according to Example2 of the present invention during focusing on an object at infinity.

FIG. 10 is a diagram of aberrations of the zoom lens according toExample 2 of the present invention during focusing on an object at afinite distance.

FIG. 11 is a diagram of aberrations of the zoom lens according toExample 3 of the present invention during focusing on an object atinfinity.

FIG. 12 is a diagram of aberrations of the zoom lens according toExample 3 of the present invention during focusing on an object at afinite distance.

FIG. 13 is a diagram of aberrations of the zoom lens according toExample 4 of the present invention during focusing on an object atinfinity.

FIG. 14 is a diagram of aberrations of the zoom lens according toExample 4 of the present invention during focusing on an object at afinite distance.

FIG. 15 is a diagram of aberrations of the zoom lens according toExample 5 of the present invention during focusing on an object atinfinity.

FIG. 16 is a diagram of aberrations of the zoom lens according toExample 5 of the present invention during focusing on an object at afinite distance.

FIG. 17 is a perspective view of an imaging apparatus according to theembodiment of the present invention when viewed from a front side.

FIG. 18 is a perspective view of an imaging apparatus according to theembodiment of the present invention when viewed from a rear side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to drawings. FIG. 1 is a cross-sectional view illustrating alens configuration of a zoom lens of an embodiment of the presentinvention at the wide-angle end. FIG. 2 is a cross-sectional viewadditionally illustrating optical paths of the zoom lens in therespective states. The examples shown in FIGS. 1 and 2 correspond to thezoom lens of Example 1 to be described later. FIGS. 1 and 2 each show astate where the object at infinity is in focus, where the left side ofthe drawing is the object side and the right side of the drawing is theimage side. In FIG. 2 , the upper part labeled by “WIDE” shows thewide-angle end state, the middle part labeled by “MIDDLE” shows themiddle focal length state, and the lower part labeled by “TELE” showsthe telephoto end state. FIG. 2 shows rays including on-axis rays wa andrays with the maximum angle of view wb at the wide-angle end state,on-axis rays ma and rays with the maximum angle of view mb at the middlefocal length state, and on-axis rays to and rays with the maximum angleof view tb at the telephoto end state. Hereinafter, the description willbe primarily made with reference to FIG. 1 .

In FIG. 1 , it is assumed that the zoom lens is applied to the imagingapparatus, and an example in which an optical member PP having anincident surface and an exit surface parallel to each other is disposedbetween the zoom lens and the image plane Sim is illustrated. Theoptical member PP is a member assumed to include various filters and/ora cover glass. The various filters are, for example, a low-pass filter,an infrared cut filter, and a filter for cutting a specific wavelengthrange. The optical member PP is a member having no refractive power, andmay be omitted.

The zoom lens of the present embodiment comprises only six lens groups,as lens groups, which consist of a first lens group G1 having a positiverefractive power, a second lens group G2 having a negative refractivepower, a third lens group G3 having a positive refractive power, afourth lens group G4 having a negative refractive power, a fifth lensgroup G5 having a negative refractive power, and a sixth lens group G6having a positive refractive power in order from the object side to theimage side along the optical axis Z. All distances between the adjacentlens groups in the optical axis direction change during zooming from thewide-angle end to the telephoto end. In such a configuration, there isan advantage in shortening the total length of the lens. Morespecifically, in such a configuration, it is possible to reduce themovement amount of the lens groups during zooming, and it is possible toshorten the total length of the lens. There is an advantage in achievinga high zoom ratio while securing telecentric properties. Particularly,in a case where the zoom lens according to the present embodiment isapplied to a mirrorless camera having short backfocus, these advantagesare more remarkable.

In the example of FIG. 1 , all the lens groups move in the optical axisdirection with different loci during zooming from the wide-angle end tothe telephoto end. In FIG. 1 , a schematic movement locus of each lensgroup during zooming from the wide-angle end to the telephoto end isindicated by a curved arrow under each lens group.

In the zoom lens according to the present embodiment, an aperture stopSt is disposed between a lens surface of the second lens group G2closest to the image side and a lens surface of the fourth lens group G4closest to the image side. There is an advantage in reducing thediameter of the lens by disposing the aperture stop St in this mannerMore specifically, it is preferable that the aperture stop St isdisposed between the lens surface of the second lens group G2 closest tothe image side and a lens surface of the third lens group G3 closest tothe object side, as shown in the example of FIG. 1 . In such a case,since the aperture stop St is located between the lens group and thelens group, there is an advantage in securing the distance between thelens groups and the distance between the aperture stop St and the lensgroup, and there is an advantage in reducing the diameter of the lensclosest to the object side.

The lens group moving during focusing (hereinafter, referred to as afocus group) is only the fourth lens group G4, and the fourth lens groupG4 is configured to move toward the image side during focusing from anobject with a long range to an object with a short range. An arrowpointing an image-side direction under the fourth lens group G4 of FIG.1 means that the fourth lens group G4 moves toward the image side duringfocusing from the object at infinity to the object with a short range.Since the fourth lens group G4 is the lens group immediately behind thelens surface of the third lens group G3 having the positive refractivepower which is closest to the image side, it is possible to reduce thesize of the lens in the diameter direction, and it is easy to reduce theweight of the lens. Accordingly, there is an advantage for high-speedfocusing. It is easy to reduce fluctuation in aberration and fluctuationin angle of view during focusing by using the fourth lens group G4 asthe focus group.

The first lens group G1 has the positive refractive power as a whole.The lens group closest to the object side is the positive lens group,and thus, there is an advantage in shortening the total length of thelens. Accordingly, it is easy to reduce the size of the lens. The firstlens group G1 consists of three lenses composed of a negative lens, apositive lens, and a positive lens in order from the object side to theimage side. It is possible to correct longitudinal chromatic aberration,lateral chromatic aberration, and spherical aberration by using thenegative lens closest to the object side. The first lens group G1 hasthe two positive lenses, and thus, it is possible to secure the positiverefractive power of the first lens group G1 while suppressing theoccurrence of the spherical aberration. Accordingly, it is possible toshorten the total length of the lens. In the example of FIG. 1 , thefirst lens group G1 consists of three lenses such as a negative lensL11, a positive lens L12, and a positive lens L13 in order from theobject side to the image side.

The second lens group G2 has the negative refractive power as a whole.The second lens group G2 is the negative lens group, and thus, thesecond lens group G2 can have a main function of zooming. In the exampleof FIG. 1 , the second lens group G2 consists of four lenses such as anegative lens L21, a negative lens L22, a positive lens L23, and anegative lens L24 in order from the object side to the image side.

The third lens group G3 has the positive refractive power as a whole.The third lens group G3 is the positive lens group, and thus, the thirdlens group G3 can have a main positive refractive function of the entiresystem. In the example of FIG. 1 , the third lens group G3 consists offive lenses such as a positive lens L31, a positive lens L32, a negativelens L33, a positive lens L34, and a positive lens L35 in order from theobject side to the image side.

It is preferable that the lens of the third lens group G3 closest to theobject side is the positive lens. In such a case, divergent rays fromthe second lens group G2 are received by the positive lens of the thirdlens group G3 closest to the object side, and thus, it is possible torestrain the diameter of the lens closer to the image side from beingfurther enlarged than the diameter of this positive lens. There is anadvantage in suppressing the occurrence of the spherical aberration.

It is preferable that the lens of the third lens group G3 closest to theimage side is the positive lens. In such a case, there is an advantagein reducing the lens diameter of the fourth lens group G4 which is thefocus group.

In a case where the lens of the third lens group G3 closest to the imageside is the positive lens, it is preferable that image shake correctionis performed by moving the positive lens of the third lens group G3closest to the image side in the direction crossing the optical axis Z.That is, it is preferable that the lens group moving during the imageshake correction (hereinafter, referred to as an anti-vibration lensgroup) consists of the positive lens of the third lens group G3 closestto the image side. Assuming that an image forming magnification of theanti-vibration lens group is βs and a combination image formingmagnification of the lens group closer to the image side than theanti-vibration lens group is βr, anti-vibration sensitivity is expressedby (1−βs)×βr. In the group configuration of the zoom lens according tothe present embodiment, an image forming magnification of the positivelens of the third lens group G3 closest to the image side tends to benegative and combination image forming magnification of the fourth lensgroup G4 to the sixth lens group G6 tend to be positive. In this regard,in a case where the positive lens of the third lens group G3 closest tothe image side is the anti-vibration lens group, the zoom lens isoptimized for securing sensitivity related to anti-vibration, and it ispossible to reduce the movement amount of the anti-vibration lens groupduring the image shake correction. Accordingly, it is possible to reducethe fluctuation in aberration during the image shake correction. In theexample of FIG. 1 , the lens L35 is the anti-vibration lens group, andan up-down arrow under the lens group L35 of FIG. 1 means that the lensL35 is the anti-vibration lens group.

It is preferable that the third lens group G3 consists of five lensessuch as a single lens having a positive refractive power, a single lenshaving a positive refractive power, a cemented lens obtained bycementing the negative lens and the positive lens in order from theobject side, and a single lens having a positive refractive power inorder from the object side to the image side. In such a case, it is easyto reduce the diameter of the lens, and it is easy to suppress theoccurrence of the spherical aberration and the longitudinal chromaticaberration.

Assuming that the third lens group G3 preferably consists of the fivelenses, it is possible to acquire the following advantages morespecifically. The divergent rays from the second lens group G2 aregently converted into convergent rays by these two positive lenses byusing the first and second single lenses each having the positiverefractive power which are included in the third lens group G3 from theobject side, and thus, it is possible to suppress the occurrence of thespherical aberration while restraining the diameter of the lens closerto the image side than these two positive lenses from increasing. Due tothe use of the cemented lens consisting of the third and fourth lensesof the third lens group G3 from the object side, it is possible tocorrect the longitudinal chromatic aberration, and it is possible tocorrect color blurring in the optical axis direction which is caused bythe longitudinal chromatic aberration. Off-axis rays closer to the imageside than the third lens group G3 are not able to be far away from theoptical axis Z by using the positive lens of the third lens group G3closest to the image side, and it is possible to reduce the lensdiameter of the lens group closer to the image side than the third lensgroup G3.

The fourth lens group G4 has the negative refractive power as a whole.The fourth lens group G4 is the negative lens group, and thus, it ispossible to correct fluctuation in astigmatism caused by the zooming.

It is preferable that the fourth lens group G4 consists of a cementedlens obtained by cementing a positive lens and a negative lens in orderfrom the object side. In such a case, it is possible to suppressfluctuation in color blurring during the focusing which is caused by thelateral chromatic aberration and the longitudinal chromatic aberration.The fourth lens group G4 which is the focus group consists of thecemented lens, and thus, it is possible to simplify a frame of the focusgroup. Accordingly, there is an advantage in achieving high-speedfocusing. In the example of FIG. 1 , the fourth lens group G4 consistsof two lenses including a positive lens L41 and a negative lens L42 inorder from the object side to the image side, and these lenses arecemented.

The fifth lens group G5 has the negative refractive power as a whole.The fifth lens group G5 is the negative lens group, and thus, it ispossible to correct the fluctuation in astigmatism caused by thezooming.

It is preferable that the fifth lens group G5 consists of a single lenshaving the negative refractive power. In a case where the number oflenses of the fifth lens group G5 increases, there is a concern thatinterference with a focusing drive system in the vicinity and a memberaround a mount will occur due to the complication of a frame and a cammechanism, and the lens becomes bulky in the radial direction in a casewhere there is an attempt to avoid the interference. In view of suchcircumstances, it is preferable that the fifth lens group G5 consists ofone lens. In the example of FIG. 1 , the fifth lens group G5 consists ofone lens such as a lens L51 which is a negative Meniscus lens convextoward the image side.

The sixth lens group G6 has the positive refractive power as a whole.The sixth lens group G6 is the positive lens group, and thus, it ispossible to reduce an incidence angle of rays with a peripheral angle ofview on the image plane Sim.

It is preferable that the sixth lens group G6 consists of a single lenshaving a positive refractive power. In a case where the number of lensesof the sixth lens group G6 increases and thus, a thickness increases,the refractive power of the second lens group G2 or a combinedrefractive power of the fourth lens group G4 and the fifth lens group G5needs to be strengthened in order to maintain the backfocus, and thefluctuation in spherical aberration and the fluctuation in astigmatismmay increase in a case where the refractive power is strengthened. Inview of such circumstances, it is preferable that the sixth lens groupG6 consists of one lens. In the example of FIG. 1 , the sixth lens groupG6 consists of one lens such as a lens L61 which is a positive Meniscuslens convex toward the image side.

It is preferable that all the lens surfaces of the sixth lens group G6each have a shape convex toward the image side. In a case where the zoomlens is mounted on the imaging apparatus, the combination of the zoomlens and an imaging element disposed on the image plane Sim is generallyused, and the sixth lens group G6 is the lens group closest to theimaging element in this case. In a case where the lens surface concavetoward the image side is present as a surface close to the imagingelement, since reflection rays from the member in the vicinity of theimaging element are returned to the imaging element again and arerendered to stray rays, there is an advantage in suppressing the strayrays by allowing all the lens surfaces of the sixth lens group G6 to beconvex toward the image side. Particularly, it is possible to acquire ahigh advantage in a lens system having a short backfocus such as animaging lens system mounted on the mirrorless camera.

In the zoom lens according to the present embodiment, in a state wherethe object at infinity is in focus, assuming that a lateralmagnification of the fourth lens group G4 at the telephoto end is β4T, alateral magnification of the fourth lens group G4 at the wide-angle endis β4W, a lateral magnification of the sixth lens group G6 at thetelephoto end is β6T, and a lateral magnification of the sixth lensgroup G6 at the wide-angle end is β6W, the following ConditionalExpression (1) is satisfied. By not allowing the result of ConditionalExpression (1) to be equal to or less than a lower limit, a zoomingfunction of the fourth lens group G4 is not able to be low, and it ispossible to suppress the movement amount of the lens group during thezooming from increasing. Thereby, the fluctuation in aberration duringfocusing can be suppressed. There is an advantage in shortening thebackfocus by reducing a zooming function of the sixth lens group G6. Bynot allowing the result of Conditional Expression (1) to be equal to orgreater than an upper limit, the zooming function of the fourth lensgroup G4 is not able to be high, and the rays are restrained from beingsharply bent in the fourth lens group G4. Accordingly, there is anadvantage in suppressing the fluctuation in aberration during thefocusing. In addition, in a case of a configuration in which ConditionalExpression (1-1) is satisfied, it is possible to obtain more favorablecharacteristics.1.5<(β4T/β4W)/(β6T/β6W)<2.5  (1)1.75<(β4T/β4W)/(β6T/β6W)<2.25  (1-1)

In the zoom lens according to the present embodiment, assuming that afocal length of the first lens group G1 is f1 and a focal length of thesixth lens group G6 is f6, it is preferable that the followingConditional Expression (2) is satisfied. By not allowing the result ofConditional Expression (2) to be equal to or less than a lower limit,there is an advantage in shortening the backfocus and suppressingfluctuation in incidence angle of the rays with the peripheral angle ofview on the image plane Sim. By not allowing the result of ConditionalExpression (2) to be equal to or greater than an upper limit, there isan advantage in shortening the total length of the lens at the telephotoend. In addition, in a case of a configuration in which ConditionalExpression (2-1) is satisfied, it is possible to obtain more favorablecharacteristics.0.95<f1/f6<1.9  (2)1.1<f1/f6<1.7  (2-1)

In the zoom lens according to the present embodiment, assuming that afocal length of the second lens group G2 is f2 and a focal length of thesixth lens group G6 is f6, it is preferable that the followingConditional Expression (3) is satisfied. By not allowing the result ofConditional Expression (3) to be equal to or less than a lower limit,there is an advantage in suppressing the total length of the lens whileincreasing the zoom ratio. By not allowing the result of ConditionalExpression (3) to be equal to or greater than an upper limit, there isan advantage in shortening the backfocus and suppressing the fluctuationin incidence angle of the rays with the peripheral angle of view on theimage plane Sim. In addition, in a case of a configuration in whichConditional Expression (3-1) is satisfied, it is possible to obtain morefavorable characteristics.−0.28<f2/f6<−0.11  (3)−0.25<f2/f6<−0.14  (3-1)

In the zoom lens according to the present embodiment, assuming that thelens of the third lens group G3 closest to the object side is thepositive lens and an Abbe number of the positive lens of the third lensgroup G3 closest to the object side at the d line is ν3f, it ispreferable that the following Conditional Expression (4) is satisfied.By not allowing the result of Conditional Expression (4) to be equal toor less than a lower limit, there is an advantage in correctinglongitudinal chromatic aberration. By not allowing the result ofConditional Expression (4) to be equal to or greater than an upperlimit, there is an advantage in suppressing fluctuations in lateralchromatic aberration at the wide-angle end and the telephoto end. Inaddition, in a case of a configuration in which Conditional Expression(4-1) is satisfied, it is possible to obtain more favorablecharacteristics.25<ν3f<49  (4)28<ν3f<45  (4-1)

In the zoom lens according to the present embodiment, in a case wherethe lens of the third lens group G3 closest to the image side is thepositive lens and an Abbe number of the positive lens of the third lensgroup G3 closest to the image side at the d line is ν3r, it ispreferable that the following Conditional Expression (5) is satisfied.Conditional Expression (5) is satisfied, and thus, it is possible tosuppress the occurrence amount of the lateral chromatic aberration. Inaddition, in a case of a configuration in which Conditional Expression(5-1) is satisfied, it is possible to obtain more favorablecharacteristics.57<ν3r<97  (5)62<ν3r<87  (5-1)

In the zoom lens according to the present embodiment, assuming that adistance on the optical axis between the lens surface of the third lensgroup G3 closest to the image side and the lens surface of the fourthlens group G4 closest to the object side at the wide-angle end is D34Wand a distance on the optical axis between the lens surface of the thirdlens group G3 closest to the image side and the lens surface of thefourth lens group G4 closest to the object side at the telephoto end isD34T, it is preferable that the following Conditional Expression (6) issatisfied. By not allowing the result of Conditional Expression (6) tobe equal to or less than a lower limit, since it is possible to suppressthe height of off-axis rays in the fourth lens group G4 at the telephotoend, it is possible to reduce the lens diameter of the fourth lens groupG4 which is the focus group. Accordingly, there is an advantage insecuring a space for mechanical components of the focusing drive system,achieving high-speed focusing, and reducing an outer diameter of aproduct. By not allowing the result of Conditional Expression (6) to beequal to or greater than an upper limit, it is possible to reduce thetotal length of the lens at the wide-angle end. In addition, in a caseof a configuration in which Conditional Expression (6-1) is satisfied,it is possible to obtain more favorable characteristics.0.2<D34W/D34T<1.2  (6)0.3<D34W/D34T<1  (6-1)

In the zoom lens according to the present embodiment, assuming that anaverage of Abbe numbers of the positive lenses within the first lensgroup G1 at the d line is ν1pave1, it is preferable that ConditionalExpression (7) is satisfied. Conditional Expression (7) is satisfied,and thus, there is an advantage in correcting longitudinal chromaticaberrations on a blue side at the telephoto end and in the vicinity ofthe blue side. In addition, in a case of a configuration in whichConditional Expression (7-1) is satisfied, it is possible to obtain morefavorable characteristics.67<ν1pave<97  (7)72<ν1pave<87  (7-1)

Although FIG. 1 illustrates the example in which all the six lens groupsmove during the zooming, the zoom lens according to the presentinvention may include the lens group fixed to the image plane Sim duringthe zooming as long as all distances between the adjacent lens groups inthe zoom lens change during the zooming.

FIG. 1 illustrates the example in which the optical member PP isdisposed between the lens system and the image plane Sim. However,various filters may be disposed between the lenses instead of disposingthe low-pass filter and/or the various filters for shielding rays with aspecific wavelength range between the lens system and the image planeSim, or the various filters the lens surface of any of the lenses may becoated so as to have the same functions as the various filters.

The above-mentioned preferred configurations and availableconfigurations may be arbitrary combinations, and it is preferable thatthe configurations are selectively adopted in accordance with requiredspecification. In accordance with the zoom lens according to the presentembodiment, it is possible to achieve high optical performance obtainedby satisfactorily correcting various aberrations with regard to imagingover the entire zooming range and from distant view to near view with asmall lens system suitable for small and light body such as themirrorless camera while securing the high zoom ratio. The “high zoomratio” described herein means a zoom ratio of 10 times or more.

Next, numerical examples of the zoom lens of the present invention willbe described.

EXAMPLE 1

FIGS. 1 and 2 are cross-sectional views of a zoom lens of Example 1, andan illustration method thereof is as described above. Therefore,repeated description is partially omitted herein. The zoom lens ofExample 1 consists of a first lens group G1 having a positive refractivepower, a second lens group G2 having a negative refractive power, anaperture stop St, a third lens group G3 having a positive refractivepower, a fourth lens group G4 having a negative refractive power, afifth lens group G5 having a negative refractive power, and a sixth lensgroup G6 having a positive refractive power in order from the objectside to the image side. All the lens groups move in the optical axisdirection with different loci during zooming, and the aperture stop Stmoves integrally with the third lens group G3. The first lens group G1consists of three lenses such as lenses L11 to L13 in order from theobject side to the image side, the second lens group G2 consists of fourlenses such as lenses L21 to L24 in order from the object side to theimage side, the third lens group G3 consists of five lenses such aslenses L31 to L35 in order from the object side to the image side, thefourth lens group G4 consists of two lenses such as lenses L41 and L42in order from the object side to the image side, the fifth lens group G5consists of one lens such as a lens L51, and the sixth lens group G6consists of one lens such as a lens L61. The focus group consists of thefourth lens group G4, and the fourth lens group G4 moves toward theimage side during the focusing from the object with a long range to anobject with a short range. The anti-vibration lens group consists of thelens L35. The outline of the zoom lens of Example 1 has been describedabove.

Table 1 shows basic lens data of the zoom lens of Example 1, Table 2shows variable surface distances, and Table 3 shows aspherical surfacecoefficients thereof. In Table 1, the column of Sn shows surfacenumbers. The surface closest to the object side is the first surface,and the surface numbers increase one by one toward the image side. Thecolumn of R shows radii of curvature of the respective surfaces. Thecolumn of D shows surface distances on the optical axis between therespective surfaces and the surfaces adjacent to the image side.Further, the column of Nd shows a refractive index of each constituentelement at the d line, the column of νd shows an Abbe number of eachconstituent element at the d line, and the column of θgF shows a partialdispersion ratio of each constituent element between the g line and theF line. It should be noted that the partial dispersion ratio θgF betweenthe g line and the F line of a certain lens is defined byθgF=(Ng−NF)/(NF−NC), where the refractive indexes of the lens at the gline (a wavelength of 435.8 nm (nanometers)), F line (a wavelength of486.1 nm (nanometers)), and C line (a wavelength of 656.3 nm(nanometers)) are Ng, NF, and NC, respectively.

In Table 1, reference signs of radii of curvature of surface shapesconvex toward the object side are set to be positive, and referencesigns of radii of curvature of surface shapes convex toward the imageside are set to be negative. Table 1 additionally shows the aperturestop St and the optical member PP. In Table 1, in a place of a surfacenumber of a surface corresponding to the aperture stop St, the surfacenumber and a term of (St) are noted. A value at the bottom place of D inTable 1 indicates a distance between the image plane Sim and the surfaceclosest to the image side in the table. In Table 1, the variable surfacedistances are referenced by the reference signs DD[ ], and are writteninto places of D, where object side surface numbers of distances arenoted in [ ].

In Table 2, values of the zoom ratio Zr, the focal length f of theentire system, the F number FNo., the maximum total angle of view 2ω,and the variable surface distance are based on the d line. (°) in theplace of 2ω indicates that the unit thereof is a degree. In Table 2,values in the wide-angle end state, the middle focal length state, andthe telephoto end state are respectively shown in the columns labeled byWIDE, MIDDLE, and TELE. Tables 1 and 2 are values in a state where theobject at infinity is in focus.

In Table 1, the reference sign * is attached to surface numbers ofaspherical surfaces, and numerical values of the paraxial radius ofcurvature are written into the column of the radius of curvature of theaspherical surface. In Table 3, the column of Sn shows surface numbersof aspherical surfaces, and the columns of KA and Am (m=3, 4, 5, . . . )show numerical values of the aspherical surface coefficients of theaspherical surfaces. The “E±n” (n: an integer) in numerical values ofthe aspherical surface coefficients of Table 3 indicates “×10^(±n)”. KAand Am are aspherical surface coefficients in an aspherical surfaceexpression expressed in the following expression.Zd=C×h ²/{1+(1−KA×C ² ×h ²)^(1/2) }+ΣAm×h ^(m)

Here, Zd is an aspherical surface depth (a length of a perpendicularfrom a point on an aspherical surface at height h to a plane that isperpendicular to the optical axis and contacts with the vertex of theaspherical surface),

h is a height (a distance from the optical axis to the lens surface),

C is a paraxial curvature,

KA and Am are aspherical surface coefficients, and Σ in the asphericalsurface expression means the sum with respect to m.

In data of each table, a degree is used as a unit of an angle, and mm(millimeter) is used as a unit of a length, but appropriate differentunits may be used since the optical system can be used even in a casewhere the system is enlarged or reduced in proportion. Further, each ofthe following tables shows numerical values rounded off to predetermineddecimal places.

TABLE 1 Example 1 Sn R D Nd νd θgF 1 87.31341 1.500 1.64769 33.790.59393 2 48.39202 7.086 1.49700 81.61 0.53887 3 477.38483 0.150 456.81528 5.128 1.53775 74.70 0.53936 5 246.16254 DD[5]  *6 55.362481.400 1.85400 40.38 0.56890 *7 13.70066 7.020 8 −25.12016 0.710 1.5638460.67 0.54030 9 16.72513 4.912 1.78470 26.29 0.61360 10 −96.61318 2.01011 −18.06216 0.700 1.83481 42.74 0.56490 12 −31.78051 DD[12] 13(St) ∞0.800 *14 22.13205 3.000 1.73077 40.51 0.57279 *15 −362.34440 0.220 1617.38795 5.855 1.49700 81.61 0.53887 17 −20.92786 0.150 18 −44.528090.600 1.91082 35.25 0.58224 19 11.32204 3.082 1.48749 70.24 0.53007 2022.32907 2.500 *21 17.78291 4.834 1.59522 67.73 0.54426 *22 −27.18638DD[22] 23 63.06222 2.260 1.80518 25.42 0.61616 24 −41.22773 0.6001.83481 42.74 0.56490 25 16.32477 DD[25] *26 −39.90460 1.000 1.5891361.15 0.53824 *27 −94.88059 DD[27] 28 −305.20925 4.318 1.48749 70.240.53007 29 −29.97475 DD[29] 30 ∞ 2.850 1.54763 54.99 0.55229 31 ∞ 1.000

TABLE 2 Example 1 WIDE MIDDLE TELE Zr 1.0 3.5 10.5 f 18.561 65.746194.393 FNo. 3.61 5.48 6.47 2ω(°) 79.4 23.8 8.4 DD[5] 0.800 27.12055.203 DD[12] 22.391 5.710 1.413 DD[22] 1.410 7.768 3.481 DD[25] 3.6099.805 12.474 DD[27] 1.555 12.369 20.714 DD[29] 18.560 15.026 28.237

TABLE 3 Example 1 Sn 6 7 14 15 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 6.0884124E−20 3.1609393E−20 0.0000000E+000.0000000E+00 A4 2.8326464E−05 2.9801311E−05 2.8066378E−05 6.1678411E−05A5 1.1489287E−06 5.4539706E−07 −3.4252381E−06  −2.9478889E−06  A6−2.9957092E−07  3.4300881E−09 1.8853685E−07 3.3641935E−07 A75.8467260E−10 −9.2582971E−10  1.0121366E−07 8.6043403E−08 A87.7494336E−10 −2.0891091E−09  −7.9601873E−09  −6.0738970E−09  A9−1.7916951E−13  4.2592750E−11 −3.9839618E−10  −2.7515833E−10  A10−7.0429475E−13  5.8027364E−12 3.3051389E−11 2.3660643E−11 Sn 21 22 26 27KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A30.0000000E+00 −7.8958738E−20  0.0000000E+00 0.0000000E+00 A4−5.1340861E−05  6.3190783E−06 −8.1994852E−05  −7.6635563E−05  A52.6767577E−06 3.4589922E−06 −6.2138338E−06  −4.4994630E−06  A61.9995563E−07 1.3626643E−07 2.9069889E−06 2.3717541E−06 A7−3.5718992E−08  −6.1853729E−08  5.8614043E−08 2.3574149E−08 A8−2.8828242E−09  −2.0630871E−10  −4.4557451E−08  −3.2482571E−08  A91.2759959E−10 2.7289586E−10 −2.5187227E−10  −9.6837820E−11  A101.1785166E−11 −2.0553184E−13  2.0469383E−10 1.4408906E−10

FIG. 7 shows aberration diagrams of the zoom lens of Example 1 in astate where the object at infinity is brought into focus. In FIG. 7 , inorder from the left side, spherical aberration, astigmatism, distortion,and lateral chromatic aberration are shown. In FIG. 7 , the upper partlabeled by WIDE shows a diagram of aberrations in the wide-angle endstate, the middle part labeled by MIDDLE shows a diagram of aberrationsin the middle focal length state, the lower part labeled by TELE shows adiagram of aberrations in the telephoto end state. In the sphericalaberration diagram, aberrations at the d line, the C line, the F line,and the g line are respectively indicated by the black solid line, thelong dashed line, the short dashed line, and the dashed double-dottedline. In the astigmatism diagram, aberration in the sagittal directionat the d line is indicated by the solid line, and aberration in thetangential direction at the d line is indicated by the short dashedline. In the distortion diagram, aberration at the d line is indicatedby the solid line. In the lateral chromatic aberration diagram,aberrations at the C line, the F line, and the g line are respectivelyindicated by the long dashed line, the short dashed line, and the dasheddouble-dotted line. In the spherical aberration diagram, FNo. indicatesan F number. In the other aberration diagrams, ω indicates a half angleof view.

FIG. 8 shows aberration diagrams of the zoom lens of Example 1 in astate where an object at a finite distance is brought into focus. FIG. 8shows the aberration diagrams in a state where an object at a distanceof 1.5 meters (m) from the image plane Sim is brought into focus, andthe illustration method and the meanings of reference signs are the sameas those in FIG. 7 .

Reference signs, meanings, description methods, illustration methods ofthe respective data pieces related to Example 1 are the same as those inthe following examples unless otherwise noted. Therefore, in thefollowing description, repeated description will be omitted.

EXAMPLE 2

FIG. 3 is a cross-sectional view of a zoom lens of Example 2. The zoomlens of Example 2 has the same configuration as the outline of the zoomlens of Example 1. Table 4 shows basic lens data of the zoom lens ofExample 2, Table 5 shows specification and variable surface distances,and Table 6 shows aspherical surface coefficients. FIG. 9 showsaberration diagrams in a state where the object at infinity is in focus,and FIG. 10 shows aberration diagrams in a state where the object at thedistance of 1.5 meters (m) from the image plane Sim is in focus.

TABLE 4 Example 2 Sn R D Nd νd θgF 1 89.36116 1.500 1.64769 33.790.59393 2 48.66208 7.184 1.49700 81.61 0.53887 3 624.11772 0.150 455.66700 5.285 1.53775 74.70 0.53936 5 251.45782 DD[5]  *6 73.695911.400 1.85400 40.38 0.56890 *7 14.22386 7.396 8 −24.86145 0.710 1.5638460.67 0.54030 9 18.18643 4.958 1.78470 26.29 0.61360 10 −68.22820 1.87011 −19.14171 0.700 1.83481 42.74 0.56490 12 −34.55352 DD[12] 13(St) ∞0.800 14 19.48184 3.286 1.72047 34.71 0.58350 15 −3912.53507 0.150 *1617.77430 4.284 1.49700 81.61 0.53887 *17 −35.22151 0.150 18 −59.856280.600 1.85025 30.05 0.59797 19 11.59025 3.066 1.51823 58.90 0.54567 2018.47849 2.500 *21 16.06916 5.990 1.49700 81.61 0.53887 *22 −20.77514DD[22] 23 57.40271 2.494 1.80809 22.76 0.63073 24 −33.34983 0.6001.85150 40.78 0.56958 25 17.26158 DD[25] *26 −51.63355 1.000 1.8540040.38 0.56890 *27 −427.82387 DD[27] 28 −303.58843 4.753 1.48749 70.240.53007 29 −26.87050 DD[29] 30 ∞ 2.850 1.54763 54.99 0.55229 31 ∞ 1.000

TABLE 5 Example 2 WIDE MIDDLE TELE Zr 1.0 3.5 10.5 f 18.549 65.706194.273 FNo. 3.61 5.58 6.43 2ω(°) 80.0 24.0 8.4 DD[5] 0.800 26.07353.559 DD[12] 23.091 6.231 1.439 DD[22] 1.402 6.582 2.087 DD[25] 3.4487.369 12.095 DD[27] 1.548 15.478 20.112 DD[29] 18.059 16.832 31.176

TABLE 6 Example 2 Sn 6 7 16 17 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 1.4872458E−20 −1.5804696E−20 0.0000000E+00 −5.9219054E−20  A4 9.9880950E−06 7.2736120E−066.4561280E−06 6.8506153E−05 A5 1.0183724E−06 9.1467469E−07−1.3805838E−06  2.3334448E−08 A6 −1.3595997E−07  −5.6732135E−08 5.0858641E−08 −4.2891278E−07  A7 2.4135596E−09 5.0591126E-09 2.0486473E−08 3.4189402E−08 A8 1.8300736E−10 −4.5633190E−10 −1.4160040E−09  −1.1728770E−09  A9 −5.5441720E−12  3.0779628E−11−6.8076020E−11  −8.4177376E−11  A10 −3.7447432E−16  1.2345846E−125.7894643E−12 9.2937990E−12 Sn 21 22 26 27 KA 1.0000000E+001.0000000E+00 1.0000000E+00 1.0000000E+00 A3 3.9479369E−20 0.0000000E+000.0000000E+00 0.0000000E+00 A4 −6.4459157E−05  1.9607623E−05−2.5669774E−05  −1.7288557E−05  A5 4.8073849E−06 4.4354601E−063.5513019E−06 3.2501027E−06 A6 −3.3875873E−07  −2.3548343E−07 7.2615198E−07 4.2668168E−07 A7 −5.8082826E−08  −6.1152334E−08 −1.3248243E−07  −8.6652444E−08  A8 3.6898225E−09 3.5717402E−09−9.7776723E−09  −7.6715578E−09  A9 1.9062263E−10 2.6590608E−107.5444907E−10 4.4569658E−10 A10 −8.4962899E−12  −1.1516071E−11 3.5388901E−11 3.8844240E−11

EXAMPLE 3

FIG. 4 is a cross-sectional view of a zoom lens of Example 3. The zoomlens of Example 3 has the same configuration as the outline of the zoomlens of Example 1. Table 7 shows basic lens data of the zoom lens ofExample 3, Table 8 shows specification and variable surface distances,and Table 9 shows aspherical surface coefficients. FIG. 11 showsaberration diagrams in a state where the object at infinity is in focus,and FIG. 12 shows aberration diagrams in a state where the object at adistance of 1.5 meters (m) from the image plane Sim is in focus.

TABLE 7 Example 3 Sn R D Nd νd θgF 1 84.35548 1.500 1.66680 33.050.59578 2 49.86137 7.135 1.49700 81.61 0.53887 3 914.30159 0.150 455.41642 5.088 1.49700 81.61 0.53887 5 219.05663 DD[5]  *6 77.547381.400 1.85400 40.38 0.56890 *7 14.00511 7.482 8 −23.40369 0.710 1.5174252.43 0.55649 9 21.27185 4.309 1.84666 23.78 0.62054 10 −82.99347 1.97511 −18.93869 0.700 1.83481 42.74 0.56490 12 −34.84765 DD[12] 13(St) ∞0.800 *14 18.10721 3.000 1.68948 31.02 0.59874 *15 166.66591 0.150 1620.04253 4.615 1.48749 70.24 0.53007 17 −26.40357 0.150 18 −81.010700.600 1.85025 30.05 0.59797 19 11.04283 3.759 1.48749 70.24 0.53007 2020.77056 2.000 *21 15.59120 5.316 1.49700 81.61 0.53887 *22 −22.66772DD[22] 23 58.90229 2.260 1.80809 22.76 0.63073 24 −56.84010 0.6001.83481 42.74 0.56490 25 16.70752 DD[25] *26 −52.64194 1.000 1.5831359.38 0.54237 *27 −465.69662 DD[27] 28 −268.68277 4.238 1.48749 70.240.53007 29 −30.27833 DD[29] 30 ∞ 2.850 1.54763 54.99 0.55229 31 ∞ 1.000

TABLE 8 Example 3 WIDE MIDDLE TELE Zr 1.0 3.5 10.5 f 18.562 65.752194.408 FNo. 3.61 5.45 6.50 2ω(°) 79.6 23.8 8.4 DD[5] 0.800 25.33354.582 DD[12] 22.927 4.526 1.436 DD[22] 1.485 8.591 2.463 DD[25] 3.5628.538 12.273 DD[27] 1.563 11.237 22.683 DD[29] 18.947 16.893 28.982

TABLE 9 Example 3 Sn 6 7 14 15 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 5.9489831E−20 3.9511741E−21 0.0000000E+00−7.8958738E−20  A4 3.3317471E−05 3.0882086E−05 2.9397718E−057.1465901E−05 A5 −1.0602309E−06  −1.8307406E−06  −4.3654816E−06 −4.9256857E−06  A6 −1.8424144E−07  2.6184353E−08 1.7942032E−075.6723298E−07 A7 1.2871194E−08 5.8190261E−09 1.2213072E−07 8.6738357E−08A8 −6.1153209E−11  −9.7055271E−10  −9.7640910E−09  −8.7847359E−09  A9−1.8149390E−11  7.7475782E−12 −4.9894742E−10  −3.3351354E−10  A106.7379815E−13 1.3073137E−13 4.2884152E−11 2.9522644E−11 Sn 21 22 26 27KA  1.0000000E+00 1.0000000E+00  1.0000000E+00 1.0000000E+00 A3 1.1843811E−19 0.0000000E+00 −8.6736174E−20 0.0000000E+00 A4−6.7317725E−05 1.2230681E−05 −1.6512370E−04 −1.4948073E−04  A5 6.9008062E−06 8.3632239E−06  1.4807192E−05 1.1190323E−05 A6−6.4244335E−07 −8.0693892E−07   1.5665174E−06 1.8223591E−06 A7−9.9583275E−09 −1.5523467E−08  −3.1692500E−07 −3.0535606E−07  A8 6.4411699E−09 7.6978380E−09 −1.8203805E−09 −3.3842656E−09  A9−2.6847434E−10 −2.8383497E−10   1.4765209E−09 1.6966984E−09 A10−1.4111654E−11 6.6584360E−12 −5.2262792E−11 −5.4110442E−11  A11 1.1510986E−12 1.5517724E−12 A12 −1.4260736E−14 −1.4214960E−13 

EXAMPLE 4

FIG. 5 is a cross-sectional view of a zoom lens of Example 4. The zoomlens of Example 4 has the same configuration as the outline of the zoomlens of Example 1. A lens L21 of Example 4 is a complex aspherical lens.Table 10 shows basic lens data of the zoom lens of Example 4, Table 11shows specification and variable surface distances, and Table 12 showsaspherical surface coefficients. FIG. 13 shows aberration diagrams in astate where the object at infinity is in focus, and FIG. 14 showsaberration diagrams in a state where the object at a distance of 1.5meters (m) from the image plane Sim is in focus.

TABLE 10 Example 4 Sn R D Nd νd θgF 1 84.75133 1.500 1.73800 32.330.59005 2 52.84624 7.075 1.49700 81.61 0.53887 3 958.80303 0.150 454.96431 5.179 1.49700 81.61 0.53887 5 227.11481 DD[5]  *6 75.179950.200 1.51876 54.04 0.55938 7 59.06751 1.400 1.83400 37.21 0.58082 813.71704 7.788 9 −22.12760 0.710 1.51742 52.43 0.55649 10 21.83549 4.4971.84666 23.78 0.62054 11 −60.71171 1.601 12 −20.32028 0.700 1.8348142.74 0.56490 13 −44.87909 DD[13] 14(St) ∞ 0.800 *15 18.16669 3.0001.68948 31.02 0.59874 *16 170.88517 0.150 17 20.03989 4.685 1.4874970.24 0.53007 18 −25.36075 0.150 19 −71.95304 0.600 1.85025 30.050.59797 20 10.95195 3.189 1.48749 70.24 0.53007 21 21.95796 2.000 *2215.75973 5.140 1.49700 81.61 0.53887 *23 −22.63864 DD[23] 24 66.448482.260 1.80809 22.76 0.63073 25 −47.06499 0.600 1.83481 42.74 0.56490 2617.10792 DD[26] *27 −57.72176 1.000 1.53409 55.87 0.55858 *28 −366.83956DD[28] 29 −113.50432 3.597 1.48749 70.24 0.53007 30 −29.29827 DD[30] 31∞ 2.850 1.54763 54.99 0.55229 32 ∞ 1.000

TABLE 11 Example 4 WIDE MIDDLE TELE Zr 1.0 3.7 10.5 f 18.562 68.444194.405 FNo. 3.61 5.53 6.51 2ω(°) 79.6 22.8 8.4 DD[5] 0.800 26.01955.209 DD[13] 23.482 4.156 1.406 DD[23] 1.429 8.474 2.459 DD[26] 3.44510.757 11.964 DD[28] 1.560 9.159 21.872 DD[30] 19.547 17.578 28.771

TABLE 12 Example 4 Sn 6 15 16 KA 1.0000000E+00 1.0000000E+001.0000000E+00 A3 1.4872458E−20 −1.5791748E−19  7.8958738E−20 A41.4293606E−05 2.6289170E−05 6.8586051E−05 A5 −7.6243133E−08 −2.7829674E−06  −3.6000591E−06  A6 −4.2898093E−08  5.1250899E−085.3894761E−07 A7 3.5373115E−09 1.1726524E−07 6.9479853E−08 A8−1.4330250E−10  −8.7067361E−09  −6.9900114E−09  A9 −3.4679000E−12 −4.8315943E−10  −2.8763740E−10  A10 4.9657578E−13 4.0422146E−112.3285042E−11 Sn 22 23 27 28 KA  1.0000000E+00  1.0000000E+001.0000000E+00 1.0000000E+00 A3 −5.9219054E−20 −3.9479369E−20−4.3368087E−20  0.0000000E+00 A4 −6.9532205E−05  8.9556622E−06−1.2945188E−04  −1.1219871E−04  A5  6.8042964E−06  8.7459941E−061.0229474E−05 6.5487738E−06 A6 −5.7873869E−07 −8.8567872E−071.6185768E−06 1.8009706E−06 A7 −2.7316586E−08 −1.8628087E−08−1.9338886E−07  −1.9588467E−07  A8  8.3795341E−09  9.7387874E−09−1.2599121E−08  −1.1267627E−08  A9 −1.0053801E−10 −3.3602579E−107.6038947E−10 1.0637196E−09 A10 −4.1478234E−11 −6.3837227E−122.8909648E−11 2.8061860E−12 A11  7.0783164E−13  1.8603707E−12 A12 7.4114490E−14 −1.1884796E−13

EXAMPLE 5

FIG. 6 is a cross-sectional view of a zoom lens of Example 5. The zoomlens of Example 5 has the same configuration as the outline of the zoomlens of Example 1. A lens L21 of Example 5 is a complex aspherical lens.Table 13 shows basic lens data of the zoom lens of Example 5, Table 14shows specification and variable surface distances, and Table 15 showsaspherical surface coefficients. FIG. 15 shows aberration diagrams in astate where the object at infinity is in focus, and FIG. 16 showsaberration diagrams in a state where the object at a distance of 1.5meters (m) from the image plane Sim is in focus.

TABLE 13 Example 5 Sn R D Nd νd θgF 1 84.71081 1.500 1.73800 32.330.59005 2 53.55987 7.418 1.49700 81.61 0.53887 3 1450.19213 0.150 457.75495 5.173 1.49700 81.61 0.53887 5 220.51162 DD[5]  *6 66.038260.300 1.51876 54.04 0.55938 7 56.39697 1.200 1.83400 37.21 0.58082 813.47361 8.109 9 −21.76017 0.710 1.51742 52.43 0.55649 10 21.70418 4.3821.84666 23.78 0.62054 11 −70.75984 1.698 12 −20.07004 0.700 1.8348142.74 0.56490 13 −38.17740 DD[13] 14(St) ∞ 0.800 *15 17.29640 3.0001.68948 31.02 0.59874 *16 166.67583 0.150 17 20.98487 4.591 1.4874970.24 0.53007 18 −25.06299 0.150 19 −81.19765 0.600 1.85025 30.050.59797 20 10.48395 3.308 1.48749 70.24 0.53007 21 21.62271 2.000 *2215.86412 4.901 1.49700 81.61 0.53887 *23 −23.67940 DD[23] 24 53.834322.047 1.80809 22.76 0.63073 25 −68.74251 0.600 1.83481 42.74 0.56490 2616.15453 DD[26] *27 −57.53685 1.000 1.53409 55.87 0.55858 *28−2502.20531 DD[28] 29 −87.97978 3.832 1.48749 70.24 0.53007 30 −25.34770DD[30] 31 ∞ 2.850 1.54763 54.99 0.55229 32 ∞ 1.000

TABLE 14 Example 5 WIDE MIDDLE TELE Zr 1.0 3.7 10.5 f 18.558 68.429194.361 FNo. 3.61 5.74 6.49 2ω(°) 78.2 23.0 8.4 DD[5] 0.800 24.71957.136 DD[13] 23.274 3.764 1.426 DD[23] 1.471 8.416 1.809 DD[26] 3.53310.983 17.232 DD[28] 1.563 8.603 15.094 DD[30] 19.216 20.370 30.324

TABLE 15 Example 5 Sn 6 15 16 KA 1.0000000E+00  1.0000000E+001.0000000E+00 A3 −2.4276014E−20  −4.3368087E−20 0.0000000E+00 A41.5475841E−05  2.0837324E−05 6.8845365E−05 A5 −3.3812045E−07 −1.9902782E−06 −3.6824306E−06  A6 −2.0599396E−08  −2.8749911E−073.6192735E−07 A7 5.6685427E−09  1.3036548E−07 8.8192414E−08 A8−4.4293362E−10  −5.8373906E−09 −7.5020753E−09  A9 3.6537360E−12−7.3377011E−10 −5.1711433E−10  A10 6.0644102E−13  1.2198849E−118.0889195E−12 Sn 22 23 27 28 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 1.3877788E−18 1.3877788E−18 0.0000000E+000.0000000E+00 A4 −4.0743079E−05  3.1529520E−05 −2.3107642E−04 −2.1034145E−04  A5 −1.6352409E−05  −7.8595749E−06  2.1633360E−051.7578744E−05 A6 9.9720128E−06 5.8233200E−06 2.3121322E−06 2.2445862E−06A7 −2.6703164E−06  −1.7176068E−06  −4.6603486E−07  −4.0212625E−07  A83.8909131E−07 2.7120790E−07 −5.4648501E−09  −6.1941686E−09  A9−3.0321710E−08  −2.2614184E−08  2.1319079E−09 2.2341188E−09 A109.8325654E−10 7.8431226E−10 −1.9106189E−11  −4.3519710E−11 

Table 16 shows values corresponding to Conditional Expressions (1) to(7) of the zoom lenses of Examples 1 to 5. In Examples 1 to 5, the dline is set as the reference wavelength. Table 16 shows the values onthe d line basis.

TABLE 16 Expres- sion Exam- Exam- Exam- Exam- Exam- Number ple 1 ple 2ple 3 ple 4 ple 5 (1) (β4T/β4W)/ 1.91 2.19 1.87 1.78 2.00 (β6T/β6W) (2)f1/f6 1.41 1.54 1.36 1.20 1.37 (3) f2/f6 −0.19 −0.22 −0.19 −0.17 −0.19(4) ν3f 40.51 34.71 31.02 31.02 31.02 (5) ν3r 67.73 81.61 81.61 81.6181.61 (6) D34W/D34T 0.41 0.67 0.60 0.58 0.81 (7) ν1pave 78.15 78.1581.61 81.61 81.61

As can be seen from the above data, in the zoom lens of Examples 1 to 5,the high zoom ratio is ensured such that the zoom ratio is equal to orgreater than 10, reduction in size is achieved, and various aberrationsare satisfactorily corrected with regard to imaging over the entirezooming range and from distant view to near view. Accordingly, highoptical performance is achieved.

Next, an imaging apparatus according to an embodiment of the presentinvention will be described. FIGS. 17 and 18 are external views of acamera 30 which is the imaging apparatus according to the embodiment ofthe present invention. FIG. 17 is a perspective view in a case where thecamera 30 is viewed from the front side, and FIG. 18 is a perspectiveview in a case where the camera 30 is viewed from the rear side. Thecamera 30 is a mirrorless digital camera to which an interchangeablelens 20 is detachably attached. The interchangeable lens 20 includes thezoom lens 1 according to the embodiment of the present invention whichis accommodated in a lens barrel.

The camera 30 comprises a camera body 31, and a shutter button 32 and apower button 33 are provided on the upper surface of the camera body 31.A manipulation unit 34, a manipulation unit 35, and a display unit 36are provided on the rear surface of the camera body 31. The display unit36 displays a captured image and an image within an angle of view beforethe image is captured.

An imaging opening on which rays from an imaging target are incident isformed in the central portion of the front surface of the camera body31, a mount 37 is provided in a position corresponding to the imagingopening, and the interchangeable lens 20 is attached to the camera body31 through the mount 37.

An imaging element such as a charge coupled device (CCD) or acomplementary metal oxide semiconductor (CMOS) that outputs imagingsignals corresponding to a subject image formed by the interchangeablelens 20, a signal processing circuit that generates an image byprocessing the imaging signals output from the imaging element, and arecording medium for recording the generated image are provided withinthe camera body 31. In the camera 30, it is possible to image a stillimage or a motion picture by pressing the shutter button 32, and imagedata obtained through the imaging is recorded in the recording medium.

The present invention has been hitherto described through embodimentsand examples, but the present invention is not limited to theabove-mentioned embodiments and examples, and may be modified intovarious forms. For example, values such as the radius of curvature, thesurface distance, the refractive index, the Abbe number, and theaspherical surface coefficient of each lens are not limited to thevalues shown in the numerical examples, and different values may be usedtherefor.

The imaging apparatus according to the embodiment of the presentinvention is not limited to the examples. For example, various aspectssuch as cameras other than non-reflex cameras, film cameras, videocameras, movie shooting cameras, and broadcasting cameras may be used.

What is claimed is:
 1. A zoom lens comprising: only six lens groups, aslens groups, which consist of a first lens group having a positiverefractive power, a second lens group having a negative refractivepower, a third lens group having a positive refractive power, a fourthlens group having a negative refractive power, a fifth lens group havinga negative refractive power, and a sixth lens group having a positiverefractive power, in order from an object side to an image side, whereinall distances between adjacent lens groups in an optical axis directionchange during zooming, a stop is disposed between a lens surface of thesecond lens group closest to the image side and a lens surface of thefourth lens group closest to the image side, the first lens groupconsists of a negative lens, a positive lens, and a positive lens inorder from the object side to the image side, and a lens group movingduring focusing is only the fourth lens group, and the fourth lens groupmoves to the image side during focusing from an object with a long rangeto an object with a short range, wherein a lens of the third lens groupclosest to the object side is a positive lens, and assuming that an Abbenumber of the positive lens of the third lens group closest to theobject side at a d line is ν3f, Conditional Expression (4) is satisfied,25<ν3f<49  (4), and wherein assuming that an average of Abbe numbers ofpositive lenses within the first lens group at a d line is ν1pave,Conditional Expression (7) is satisfied,67<ν1pave<97  (7).
 2. The zoom lens according to claim 1, whereinassuming that a focal length of the first lens group is f1 and a focallength of the sixth lens group is f6, Conditional Expression (2) issatisfied,0.95<f1/f6<1.9  (2).
 3. The zoom lens according to claim 1, whereinassuming that a focal length of the second lens group is f2 and a focallength of the sixth lens group is f6, Conditional Expression (3) issatisfied,−0.28<f2/f6<−0.11  (3).
 4. The zoom lens according to claim 1, wherein alens of the third lens group closest to the image side is a positivelens, and assuming that an Abbe number of the positive lens of the thirdlens group closest to the image side at a d line is ν3r, ConditionalExpression (5) is satisfied,57<ν3r<97  (5).
 5. The zoom lens according to claim 1, wherein assumingthat a distance on an optical axis between a lens surface of the thirdlens group closest to the image side at a wide-angle end and a lenssurface of the fourth lens group closest to the object side at thewide-angle end is D34W and a distance on the optical axis between a lenssurface of the third lens group closest to the image side at a telephotoend and a lens surface of the fourth lens group closest to the objectside at the telephoto end is D34T, Conditional Expression (6) issatisfied,0.2<D34W/D34T<1.2  (6).
 6. The zoom lens according to claim 1, whereinthe third lens group consists of a single lens having a positiverefractive power, a single lens having a positive refractive power, acemented lens obtained by cementing a negative lens and a positive lensin order from the object side, and a single lens having a positiverefractive power in order from the object side to the image side.
 7. Thezoom lens according to claim 1, wherein the fourth lens group consistsof a cemented lens obtained by cementing a positive lens and a negativelens in order from the object side.
 8. The zoom lens according to claim1, wherein the fifth lens group consists of a single lens having anegative refractive power.
 9. The zoom lens according to claim 1,wherein the sixth lens group consists of a single lens having a positiverefractive power.
 10. The zoom lens according to claim 2, whereinConditional Expression (2-1) is satisfied,1.1<f1/f6<1.7  (2-1).
 11. The zoom lens according to claim 3, whereinConditional Expression (3-1) is satisfied,−0.25<f2/f6<−0.14  (3-1).
 12. The zoom lens according to claim 1,wherein Conditional Expression (4-1) is satisfied,28<ν3f<45  (4-1).
 13. The zoom lens according to claim 4, whereinConditional Expression (5-1) is satisfied,62<ν3r<87  (5-1).
 14. The zoom lens according to claim 5, whereinConditional Expression (6-1) is satisfied,0.3<D34W/D34T<1  (6-1).
 15. The zoom lens according to claim 1, whereinConditional Expression (7-1) is satisfied,72<ν1pave<87  (7-1).
 16. An imaging apparatus comprising the zoom lensaccording to claim
 1. 17. A zoom lens comprising: only six lens groups,as lens groups, which consist of a first lens group having a positiverefractive power, a second lens group having a negative refractivepower, a third lens group having a positive refractive power, a fourthlens group having a negative refractive power, a fifth lens group havinga negative refractive power, and a sixth lens group having a positiverefractive power, in order from an object side to an image side, whereinall distances between adjacent lens groups in an optical axis directionchange during zooming, a stop is disposed between a lens surface of thesecond lens group closest to the image side and a lens surface of thefourth lens group closest to the image side, the first lens groupconsists of a negative lens, a positive lens, and a positive lens inorder from the object side to the image side, and a lens group movingduring focusing is only the fourth lens group, and the fourth lens groupmoves to the image side during focusing from an object with a long rangeto an object with a short range, wherein a lens of the third lens groupclosest to the object side is a positive lens, and assuming that an Abbenumber of the positive lens of the third lens group closest to theobject side at a d line is ν3f, Conditional Expression (4) is satisfied,25<ν3f<49  (4), and wherein the fourth lens group consists of a cementedlens obtained by cementing a positive lens and a negative lens in orderfrom the object side.
 18. A zoom lens comprising: only six lens groups,as lens groups, which consist of a first lens group having a positiverefractive power, a second lens group having a negative refractivepower, a third lens group having a positive refractive power, a fourthlens group having a negative refractive power, a fifth lens group havinga negative refractive power, and a sixth lens group having a positiverefractive power, in order from an object side to an image side, whereinall distances between adjacent lens groups in an optical axis directionchange during zooming, a stop is disposed between a lens surface of thesecond lens group closest to the image side and a lens surface of thefourth lens group closest to the image side, the first lens groupconsists of a negative lens, a positive lens, and a positive lens inorder from the object side to the image side, and a lens group movingduring focusing is only the fourth lens group, and the fourth lens groupmoves to the image side during focusing from an object with a long rangeto an object with a short range, wherein a lens of the third lens groupclosest to the object side is a positive lens, and assuming that an Abbenumber of the positive lens of the third lens group closest to theobject side at a d line is ν3f, Conditional Expression (4) is satisfied,25<ν3f<49  (4), and wherein a lens of the third lens group closest tothe image side is a positive lens, and assuming that an Abbe number ofthe positive lens of the third lens group closest to the image side at ad line is ν3r, Conditional Expression (5-1) is satisfied,62<ν3r<87  (5-1).